Lesion
of the optic radiation as it approaches the occipital cortex can lead to
homonymous hemianopia which is often congruous. Lesion of the occipital
cortex may produce macular-sparing homonymous hemianopia this is most often
seen in cerebrovascular accident involving the posterior cerebral artery

Testing for macular sparing. This is done by moving a
red target form the non-seeing field into the seeing field. If the red
pin is noticed before it crosses the mid-line, macular sparing is present.

Question:How would you investigate a patient with homonymous hemianopia?